1. Field of the Invention
This invention relates to an instrument for measuring the amplitude of vibration of a vibrating object, and more particularly to an instrument for measuring the amplitude of vibration of a vibrating object wherein the amplitude of vibration is measured by means of a moire pattern.
2. Description of the Prior Art
The main methods heretofore proposed for measuring the amplitude of vibration of a vibrating object are the holographic interferometric method, the speckle interferometric method, the moire method and the dot-pattern method. Of these, the dot-pattern method has the widest range of measurement applications. This method is, however, disadvantageous is that it does not permit simple numerical evaluation of vibration amplitude and that post-measurement processing tends to be complex. The other methods, although they provide an easily readable indication of the description of vibration amplitude in the form of contour lines, are severely limited in the range of vibration amplitudes which they are capable of measuring, the holographic interferometric method being limited to the range of from about 0.1.mu. to 10.mu., the speckle interferometric method to the range of from 1.mu. to 100.mu. and the moire method to measurement of vibration amplitude of 1mm and over. Thus no existing method of measurement is responsive to amplitudes on the order of 100.mu..